Nutrient demand and availability related to growth among natural assemblages of phytoplankton

Abstract

Abstract In the summer of 1984/85 water samples from 10 Central Volcanic Plateau lakes were examined for a variety of plant nutrient components, and the plankton were subjected to three short term physiological assays which indicate nutrient demand and to a 4 d growth assay. In samples from four of the lakes plankton were exposed to a surfeit of phosphorus, for they were bathed in substantial concentrations (> 3 mg P m ‐3 ) of dissolved reactive phosphorus and their capacity to accumulate this nutrient was low ( < 10% of initial phosphorus content in 4 h), indicating that their phosphorus stores were substantially full. In samples from all 10 lakes, plankton biomass increase (measured by change in chlorophyll a concentration) was prevented by shortage of nutrient nitrogen.